For the optimum control of a starting process of a motor vehicle from standstill thereof, the mass of the motor vehicle must be known. This is particularly important with motor vehicles whose vehicle mass varies markedly, for example utility vehicles such as trucks. Only when the vehicle mass of the motor vehicle is known can a starting gear be selected correctly. Furthermore, if the vehicle mass is known, a starting clutch connected between the transmission and the drive aggregate can be controlled with precision.
Since motor vehicles such as utility vehicles do not as a rule have sensors with the help of which the vehicle's mass can be determined by direct measurement, the vehicle's mass has to be determined by computation. Thus, from DE 10 2006 022 171 A1 a method is known, with the help of which, during operation, i.e. while driving, the mass of the motor vehicle is calculated. However, such a method can only be used while driving.
Since after a motor vehicle, for example a truck, has come to rest, its mass as a rule changes due to loading and/or unloading, the mass of the motor vehicle computed in accordance with the method of DE 10 2006 022 171 A1 cannot be used for a starting process from standstill of the vehicle after restarting it. Rather, to control a starting process from standstill of the motor vehicle after it has been restarted, mass initialization values are used, namely a minimum mass value and a maximum mass value which are independent of the motor vehicle concerned.
In the methods known from the prior art, as the minimum mass value for initializing the mass of a motor vehicle after it is restarted, the unloaded weight without trailer, i.e. the mass of an unloaded tractor machine is used. On the other hand, as the maximum mass value for initializing the mass after restarting the vehicle, the mass of the motor vehicle when it is carrying its maximum permitted load is used. This procedure for initializing the mass of a motor vehicle after restarting it is inexact, so a starting gear can only be selected inaccurately. Moreover, the starting clutch can only be controlled imprecisely.